The present invention relates generally to the field of arrangements for supporting Digital Storage Elements or other such devices which are sensitive to mechanical shock and, more particularly, to a highly advantageous resilient support arrangement for isolating a Digital Storage Element from the effects of a given mechanical shock. The present invention provides additional advantages beyond mechanical shock isolation, as will be described.
As a class of devices, electromechanical digital storage arrangements are generally susceptible to mechanical shock. Hard disk drives are especially susceptible to mechanical shock during operation. In fact, upon the receipt of an electromechanical shock having a sufficient magnitude and frequency, it is well known that a hard disk drive may experience a catastrophic failure. The prior art, in coping with the potential effects of mechanical shock, has developed a number of approaches, as will be described below.
As a first example of a prior art approach which attempts to mitigate the effects of mechanical shock on a hard disk drive, rubber grommets or “doughnuts” are used in mounting arrangements. A first implementation of this approach is illustrated by FIG. 12 of U.S. Pat. No. 5,706,168, issued to Erler et al (hereinafter the '168 patent), as well as an associated description which appears at column 11, lines 15-25. A grommet or rubber doughnut is described as having a receiving groove formed on its outer periphery. The grommet further defines a central fastener receiving hole. The peripheral receiving groove is used to capture each grommet within an aperture that is itself defined within a mounting bridge. The latter, in turn, supports a hard disk drive. A threaded fastener passes through the fastener receiving hole defined by the grommet and threadingly engages a boss. Accordingly, the mounting bridge is resiliently isolated by a plurality of rubber grommets so as to, in turn, isolate the hard disk drive.
One typical and relatively simplistic implementation of the rubber grommet approach (not illustrated) does not rely on the use of a mounting bridge. Four mounting posts are threaded directly into the hard disk drive. A rubber grommet is then received on the mounting post. The host device then captures each rubber grommet about its peripheral groove, thereby providing for at least limited shock isolation.
Either implementation of the rubber grommet isolation approach is at least somewhat effective in providing mechanical shock isolation, however, it should be appreciated that a number of problems accompany its use. For example, this approach may be considered as an anisotropic mounting arrangement. That is, shock attenuation properties vary with directional orientation. In particular, the shock attenuation properties in a direction oriented along the elongation axis of the mounting post are generally completely different from the isolation properties in a plane that is transverse to the mounting post and which bisects the rubber doughnut. For a force oriented along the elongation axis, the rubber doughnut is subjected to compression, extending uniformly about the circumference of the rubber doughnut.
For all other force orientations, the rubber doughnut experiences at least some radial compression of only a portion of its circumference. Where a received force is orthogonal to a mounting post, the rubber doughnut experiences only partial radial compression. Hence, with variation of the orientation of received forces, an extremely complex multi-mode response interaction is exhibited by the rubber doughnuts ranging along a spectrum from uniform circumferential compression to partial radial compression or some combination thereof. It is submitted that it is extremely difficult to control shock isolation properties with respect to these different responses, for example, with the intent of providing equal attenuation properties in every direction. The present invention considers the rubber doughnut approach as being unacceptable in the instance where precision control of mechanical shock response is required, as will be further described at an appropriate point hereinafter.
Another approach taken by the prior art in dealing with mechanical shock is represented by U.S. Pat. No. 6,304,440 issued to Lin (hereinafter the '440 patent). The '440 patent further describes an external box for a hard disk drive that is electrically interfaceable with a host computer, rather than a support arrangement for physically receiving a storage component within a host device. The patent, however, describes a padded arrangement for housing the hard disk drive, as may be seen in its FIGS. 1 and 2 wherein a plurality of soft protecting pads 5, each of which includes a cylindrical configuration, apparently support the hard disk drive within the external hard disk drive housing. A number of the protecting pads are mounted outward of a pair of fixing blocks which are themselves affixed along three edges of the hard disk drive. The brief description within the patent appears to be devoid of any further description as to how the remaining protecting pads are attached or held in place, if indeed, they are attached in place at all. Moreover, no description has been found by Applicants which would lead Applicants to believe that the outward or free ends of any of the support pads are fixedly attached to the interior surfaces of the external case in any way. While it is admitted that cushioning is provided by the support arrangement of the '440 patent, at the same time, it is submitted that the approach of this patent is problematic for a number of reasons, as will be described immediately hereinafter.
Initially, it is submitted that the patent is devoid of any description with regard to implementing the mechanical shock protection scheme in view of a given mechanical shock force that is anticipated to be received by the external hard disk drive case. In this regard, it should be appreciated that the response of any support arrangement varies not only with the magnitude of the mechanical shock received and its directional orientation, but also with the frequency of the received shock. Still further complications are introduced since there is no description as to how many of the soft pads should be used at each surface of the hard disk drive, how the pads should be arranged or how to keep them in that arrangement. Further, no description is provided as to the material from which the soft pads are formed or for appropriately selecting suitable materials. In and by themselves, these complications create significant concerns with regard to implementing a precision shock protection arrangement.
With continuing reference to the '440 patent, the response of this arrangement is still further complicated by the outward, unconnected or free ends of the cylindrical shock pads. Since the free end of each pad is apparently intended to be held in position only by a resilient bias force afforded by the pad itself compressed between the hard disk drive and external case, maintaining any position of the free end of each pad is dependent upon the magnitude of the resilient bias force, as well as friction between the free end of the pad and the interior of the external case. When a shock of a sufficient magnitude and frequency is received, it is submitted that the free ends of the pads will slip against the external case. Upon slipping in this manner, it is uncertain whether the pads will return to their original positions. Once the free ends of the pads are randomly displaced in such a way, any predictability as to the response of this arrangement to a given mechanical shock is certainly lost. Over time, the position of the hard disk drive may shift within the external hard drive case with shifting of the free ends of the soft pads in one direction or another. Of course, further unpredictability will be encountered where the pads permanently deform into curved configurations as a result of long-term free end displacement.
Like the '168 patent, described above, providing a controlled or equal response along or about different axes is considered, at the least, to be difficult using this arrangement. For example, the soft pads must respond in different ways depending upon the directional orientation of a received mechanical force. Where the latter is normal to one of the padded sides of the hard disk drive, those pads will compressively receive the force. In contrast, a mechanical force having a component directed across diagonally opposing corners of the hard disk drive will cause bending of the pads. That is, none of the pads in the entire arrangement are solely compressed by such a diagonally oriented mechanical shock force. Thus, the pads may respond in a complex multimode manner depending upon the directional orientation of a received force. This complexity is itself problematic where it is desired to implement a precision controlled shock response arrangement.
Still another prior art approach to the problem of dealing with mechanical shock forces received by a digital storage arrangement is exemplified by published U.S. patent application No. 2001/0012175, by Williams et al., published on Aug. 9, 2001 (hereinafter Williams). The Williams publication describes a hard disk drive to which a plurality of elastomeric bumpers is attached. Each bumper includes a shank that is pressed into an aperture defined by the hard disk drive. The utility of these bumpers is described in the context of dropping the hard disk drive onto an external surface during shipment so as to produce an impact load directly received by the hard disk drive. In this regard, it should be appreciated that the Williams disclosure does not show nor describe a bumper configuration for in situ or operational use, for example, within a host device. Moreover, the Williams disclosure appears to provide no description with regard to specific design considerations in view of the hard disk drive receiving a given mechanical shock, for instance, directly onto one of the described bumpers.
It is submitted that the present invention resolves the foregoing complications, problems and concerns in highly advantageous ways while providing still further advantages.